Chapter 7              Bayesianism: How It Works

 

                                

                                             

    

                                                 

                                     Thomas Bayes (credit: Wikimedia Commons)

The best answer to the problem of what human minds and human knowing are is that, in reality, we are all Bayesians. On Bayesianism, I can build a universal moral system.

So, what is Bayesianism?

Thomas Bayes was a Presbyterian minister, statistician, and philosopher who formulated the theorem named for him: Bayes’ Theorem. His theory of how humans form tentative beliefs and gradually turn those beliefs into concepts has been given several mathematical formulations, but it says a fairly simple thing.

Bayes’ Theorem says this: we tend to become more convinced of the truth of a theory or model of reality the more we keep encountering bits of evidence that, first, support the theory and, second, can’t be explained by any of the competing theories our minds already hold.¹

Under the Bayesian model, we never claim to know anything for certain. Empiricism and Rationalism both aim to provide us with a way of thinking that can lead us to unshakable truths. But Bayesianism does not claim to seek perfect truth. Instead, it says that we hold most firmly a few beliefs we consider very highly probable, and we use them as we make decisions in our lives. We then assign lesser degrees of probability to our more peripheral beliefs, and we constantly track the evidence confirming or disconfirming all our beliefs. Under Bayesianism, we accept that all beliefs, at every level of generality, need constant updating, even the ones that have been working well at guiding us to handle real life. It is far more akin to Empiricism than Rationalism, but beyond both. Agile. Alive.

For most people, in their daily lives, the more a theory enables them to establish some kind of overall order that covers all their concepts and memories, the more persuasive the theory seems. If the evidence favoring the theory mounts, and its degree of consistency with the rest of the concepts and memories in the mind also grows, then finally, in a leap of understanding, the mind promotes the theory up to the status of a belief and incorporates the new belief into its total stock of thinking machinery. Once I understand how evolution works, I see it in every living thing I pass. The same is true of gravity, respiration, etc.

At the same time, the mind nearly always has to demote to inactive status some formerly held concepts that are not commensurable with the new belief. This is especially true of all mental activities involved in the kinds of thinking that are now being covered by the new theory. For example, once you absorb and accept a theory of how your immune system works, that concept will inform every health-related decision you make thereafter – diet, supplements, exercise, etc.

In life, examples of the workings of Bayesianism can be seen all the time. All we need do is look closely at how we and the people around us make up our minds.

When I was in junior high school, each year in June, I and all the other students of the school were bussed to the city track meet at a stadium in West Edmonton. Student athletes from all the public junior high schools in the city came to compete in the biggest track meet of the year. Its being held near the end of the school year, of course, added to the excitement of the day.

A few of the athletes competing came from a special school that educated and cared for those kids who today would be called “mentally challenged”. In my Grade 9 year, three of my friends and I, on a patch of grass beside the bleachers, did a mock cheer in which we shouted the name of this school in a short rhyming chant, attempted some clumsy dance kicks in step, crashed into each other, and fell down – all in an obviously mocking style. I should make clear that I did not learn such a cruel attitude from my home. Had they seen this stunt, my parents would have been furious. But fourteen-year-olds with their peers can be cruel.

The problem was that one of the prettiest, smartest girls in my Grade 9 class, Ann, was sitting in the bleachers, watching field events in a lull between track events. She and two of her friends happened to catch our little routine. By the glares on their faces, I could see they were not amused. Later that day, I learned that she had an older brother who had attended our school and earned excellent marks, but she also had a younger brother who had Down syndrome.

I apologized lamely the next day at school, but it was clear I’d lost all chance with her. However, she said one thing that stayed with me. She told me that if you form a bond with a mentally retarded person (retarded was the word we used in those days), you will soon realize you have made a friend whose loyalty, once won, is unchanging and unshakeable – probably, the most loyal friend you will ever have. And that realization will change you.

The idea she was expressing took root. Then, over the next twenty years, it grew into a concept and finally into an absolute conviction.

                            

                  

           

              Francis Galton, originator of eugenics (credit: Wikimedia Commons)

It was the proverbial thin edge of the wedge. Earlier, I had absorbed some of the ideas of the pseudo-science called Eugenics from one of my friends at school. I’d concluded the mentally challenged added nothing of value to a community, but inevitably took a great deal out of it. They could, and should, be bred out of the human genome. What Ann said made me question those assumptions. 

Over years of seeing movies like A Child Is Waiting and Charlie, and of being exposed to awareness-raising campaigns by families of the mentally challenged, I began to see them in a different light. Over decades of changes in attitudes, they were called mentally handicapped and then mentally challenged or special needs, and the changing terminology did matter. It changed society’s thinking.

I became a teacher, and then, in the middle of my career, mentally challenged kids began to be integrated into the public school where I taught. I saw with increasing clarity what they could teach the rest of us, just by being themselves.

Tracy was severely handicapped, mentally and physically. Trish, on the other hand, was a reasonably bright girl who had rage issues. She beat up other girls, she stole, she skipped class, she smoked pot behind the school. But when Tracy came to us, Trish proved in a few weeks to be the best with Tracy of any of the students in the school. Her attentiveness and gentleness were humbling to see. In Tracy, Trish found someone who needed her; it changed everything for Trish. As I watched them together one day, it changed me. Years of persuasion and experience, by gradual degrees, finally, got to me. I saw a new order in the community in which I lived, a new view of compassion and inclusiveness that gave coherence to years of memories. We are all siblings caring for each other in a social ecosystem.

Today, I believe the mentally challenged are people. But it was only grudgingly at fourteen that I began to re-examine my beliefs about them. At fourteen, I liked believing my mind was made up on every issue. Only years of gradually growing awareness led me to change my view. A new thinking model, gradually, by accumulation of evidence, came to look more correct and useful to me than the old model. Then, in a kind of conversion experience, I switched models. Of course, by gradual degrees, through exposure to reasonable arguments and real experiences, I and a lot of other people have come a long way on the mentally challenged from what we believed in 1964. Humans can change. By Bayesian kinds of steps, I learned a new way of looking at the mentally challenged.

 

                

                              Doberman Pinscher (credit: Wikimedia Commons) 

 

 

In a more scientific example of Bayesianism working in my own thinking, I will also mention our Doberman Pinscher–cross pup. Rex was basically a good dog, but he was a mutt, a Doberman cross we acquired because one of my aunts couldn’t keep him. People often remarked that he looked like a Doberman, but his tail was not docked. This got me curious. I learned that most Dobermans had had their tails bobbed for many generations, and I wondered why the tails, after many generations of docking, had not simply become shortened at birth. I asked a Biology teacher at my high school, but his answer only confused me. Actually, I don’t think he understood the key concepts in Darwinian Evolution Theory himself.

                                    

                               Jean-Batiste Lamarck (credit: Wikimedia Commons)

Once I got to university, I took several Biology courses. Gradually at first, and then in a breakthrough of understanding, I came to realize that I had been thinking in terms of the model of evolution called Lamarckism. At first, I did not want to let go of this cherished opinion of mine. I had always thought of myself as progressive, modern, scientific; I did not believe in Creationism. I thought I knew how evolution worked. I thought I was using an understanding of it in all my thinking. It was only after I had read more and seen by experience that docking dogs’ tails did not cause their pups’ tails to be any shorter that I came to a full understanding of Darwinian evolution.